The instant invention relates generally to an improved "front end" circuit utilized with a radio frequency receiver, and specifically to an improved front end mixer which requires less injection power withut detrimentally affecting RF signal selectability of the circuit.
In the operation of a radio frequency receiver front end, it is desirable to have high dynamic range and receiver frequency selectability, especially when the receiver is located at close range or in close frequency allocation to the RF transmitter, situations which oftentimes may "jam" the receiver. One way shown in the prior art to provide high dynamic range has been through the use of a parametric mixer-preamplifier. However, the power requirements of this circuit present a problem in the application of this type of circuit in battery operated, pack set radios and the like because of the high amount of local oscillator injection power required. The instant invention provides a mixer circuit which has a low level local oscillator injection power requirement achieved by utilizing a sampling diode bridge for the RF receiver "front end" mixer.